This invention relates generally to semiconductor packaging. More particularly, this invention relates to a method and to a system for singulating semiconductor components contained on a substrate.
Semiconductor components, such as packages, multi chip modules, printed circuit boards and interconnects are typically fabricated on a substrate which contains multiple components. The substrate can comprise a panel containing one or more rows of components, or one or more arrays of components in a matrix of rows and columns. Following the fabrication process the substrate is singulated into individual components.
BGA packages and chip scale packages, for example, can be fabricated on a substrate made of a circuit board material, such as bismaleimide triazine (BT). Typically, the singulation process is performed by cutting the substrate, such that each component includes a xe2x80x9ccomponent substratexe2x80x9d formed by a portion of the substrate. One method for cutting the substrate uses diamond tipped saw blades, similar to the blades used to dice semiconductor wafers into individual dice. In addition, the substrate can include locator openings for receiving locator pins, which are adapted to align the substrate to the saw blades during the sawing step of the singulation process.
Referring to FIGS. 1A and 1B, a prior art substrate 10A made for fabricating semiconductor components 12 is illustrated. As shown in FIG. 1A, the substrate 10A is a panel (or strip) of material similar in function to a metal leadframe. In this example, the substrate 10A comprises a circuit board material, and the components 12 comprise BGA packages arranged in a single row on the substrate 10A. However, the components 12, rather than being BGA packages, can comprise other electronic elements made with semiconductor dice, such as chip scale packages, multi chip modules or printed circuit boards. The components 12 can also comprise interconnects for electrically engaging semiconductor dice. In addition, the components 12 can be arranged in more than one row (e.g., two rows, three rows etc.).
As shown in FIG. 1B, the components 12 include an encapsulant 14 which encapsulates a semiconductor die (not shown) bonded to a first side 18 of the substrate 10A. In addition, the components 12 include external contacts 16, such as solder balls in a grid array, formed on a second side 20 of the substrate 10A in electrical communication with the die. The substrate 10A also includes locator openings 22 formed along the opposing longitudinal edges of the substrate 10A. The locator openings 22 facilitate handling of the substrate 10A by automated equipment, such as conveyors, loaders and magazines. The locator openings 22 also function to align the substrate 10A, and the components 12, on various process equipment during different fabrication processes such as singulation, die attach and wire bonding.
Referring to FIGS. 1C and 1D, a prior art matrix substrate 10B for fabricating the semiconductor components 12 is illustrated. The substrate 10B is substantially similar in construction to the substrate 10A described above. However, in this case the substrate 10B, following a singulation step, includes separate arrays 27, each of which includes multiple components 12 arranged in a matrix of rows and columns. As with the substrate 10A, the substrate 10B includes locator openings 22 that facilitate handling and alignment of the substrate 10B during fabrication of the components 12. As another alternative, the substrate can comprise a panel that contains a single matrix of components 12 rather than multiple arrays.
Referring to FIGS. 2A and 2B, a prior art system 23 for singulating the substrate 10A is illustrated. The system 23 includes a nest 24 for supporting the substrate 10A, a clamp assembly 25 for clamping the substrate 10A on the nest 24, and a sawing base 30 for holding the nest 24 during a sawing step of the singulation process.
As shown in FIG. 2B, the system 23 also includes one or more saw blades 28 configured to saw the substrate 10A into the separate components 12. The saw blades 28 rotate at high rpms, as indicated by rotational arrow 31, and are also movable in the z-direction as indicated by z-direction arrow 34. The sawing base 30 is moveable in an axial directions (e.g., x-direction) as indicated by axial direction arrow 37. The saw blades 28 are configured to saw across the lateral axis, or along the longitudinal axis of the substrate 10A, as the sawing base 30 moves the substrate 10A in axial directions as required. The sawing base 30 can also be rotated about it""s longitudinal axis (theta rotation) for positioning the substrate 10A for lateral or longitudinal sawing. Such a prior art system is manufactured by Intercon Tools, Inc. of Morgan Hill, Calif.
As shown in FIG. 2A, the nest 24 includes locator pins 26 which are placed through the locator openings 22 (FIG. 1A) in the substrate 10A. The locator openings 22 align the substrate 10A on the nest 24. As also shown in FIG. 2A, the substrate 10A is initially placed on the locator pins 26, and then clamped to the nest 24 using the clamp assembly 25.
As shown in FIG. 2B, the nest 24 is then placed on the sawing base 30, and the clamp assembly 25 is removed. The sawing base 30 includes mounting studs 36 that mate with mounting openings 38 on the nest 24, and also one or more vacuum conduits (not shown) for holding the nest 24 on the sawing base 30. The sawing base 30 also includes a pedestal 39, and a vacuum conduit 40, configured to apply a vacuum for holding the substrate 10A on the nest 24 once the clamp assembly 25 is removed. With the substrate 10A held on the nest 24, and the nest 24 held on the sawing base 30, the sawing step is performed by moving the sawing base 30 in the axial direction 37, such that the saw blades 28 saw across the width, or the length, of the substrate 10A as required.
One shortcoming of this prior art system 23 is that the locator pins 26 sometimes collect sawing scrap 32 (FIG. 2C) during the sawing step. The scrap 32 (FIG. 2C) can include pieces of the substrate 10A, as well as other debris from the sawing step. As the saw blades 28 rotate in close proximity to the locator pins 26, the scrap 32 (FIG. 2C) can come in contact with the rotating saw blades 28 causing bending, and in some cases breakage of the saw blades 28. As is apparent, the damaged saw blades 28 are expensive to replace. In addition, replacement of the saw blades 28 requires that the sawing equipment be shut down, which causes even more costly production delays.
Besides damaging the saw blades 28 the scrap 32 can also cause problems with loading of the substrate 10A into the nest 24, and with unloading of the singulated components 12 from the nest 24. These problems can also cause production delays, and require operators of the system 23 to manually remove the sawing scrap 32 from the locator pins 26.
The present invention is directed to a method and to a system for singulating semiconductor components in which locator pins are eliminated from the sawing step. Specifically, the invention includes a pre-stage alignment step in which the substrate is aligned for the sawing step. Although locator pins are used during the pre-stage alignment step, the locator pins are eliminated from the nest, such that scrap does not collect on the locator pins during the sawing step, and damage to the saw blades is reduced.
In accordance with the present invention, an improved method and system for singulating semiconductor components are provided. Also provided are an improved sawing nest for semiconductor components, and improved semiconductor components fabricated using the method and the system.
The method includes the step of providing a substrate containing the components, and including locator openings for locating and handling the substrate. The substrate can be in the form of a panel (or a strip) containing one or more single rows of components, or alternately a panel containing one or more arrays of components in a matrix of rows and columns. The method also includes the step of providing a prestage alignment base having locator pins, and a nest and clamping mechanism mountable to the prestage alignment base for holding the substrate. The prestage alignment base and the nest can be configured for use with a particular substrate, such as substrates having components in one or more rows, or substrates having one or more arrays of components in a matrix of rows and columns.
The method also includes a prestage alignment step in which the nest is mounted to the prestage alignment base and the substrate is placed on the nest. The prestage alignment base includes mounting studs that mate with mounting openings on the base. During the prestage alignment step, the locator pins on the prestage alignment base project through openings in the nest, and engage the locator openings on the substrate to align the substrate on the nest. With the substrate aligned on the nest, the clamping mechanism is attached to the nest to maintain the alignment, and the nest is removed from the prestage alignment base and mounted to a sawing base. As with the prestage alignment base, the sawing base includes mounting studs that engage the mounting openings on the nest. The sawing base also includes pedestals having vacuum conduits in flow communication with a vacuum source adapted to hold the substrate on the nest. The sawing base can also include vacuum conduits for holding the nest on the sawing base. The sawing base is movable in axial directions, and can also be rotated about it""s axis (theta rotation) for positioning the substrate for lateral or longitudinal sawing.
With the substrate held on the nest by vacuum applied through the sawing base, the clamping mechanism is removed from the nest, and a sawing step is performed using one or more saw blades. During the sawing step, the vacuum holds the substrate on the nest, and there are no locator pins to compromise the operation of the saw blades. In particular, the locator pins are contained on the prestage alignment base which is not used during the sawing step. The method thus performs a prestage alignment step with locator pins, but eliminates the locator pins from the sawing step. Following the sawing step, the vacuum can be shut off, and the singulated components can be removed from the nest using a suitable mechanism such as a pick and place mechanism. In addition, the remaining portions of the cut substrate can be removed from the nest manually, or using a suitable mechanism.
The system includes the nest and the clamping mechanism for holding the substrate, and the prestage alignment base for holding the nest. The prestage alignment base includes the mounting studs for the nest, and the locator pins projecting through openings in the nest and configured to engage the locator openings. The system also includes the sawing base, which includes the mounting studs for supporting the nest, and the pedestals with the vacuum conduits for holding the substrate stationary on the nest for sawing. The system also includes the saws, and the vacuum source in flow communication with the vacuum conduit and pedestal on the sawing base.
In an alternate embodiment system, locator pins are mounted to the prestage alignment base, and to the clamping mechanism as well.